Hitherto, in general wiring substrates used for mounting electronic components such as a semiconductor element, a sensor element, a capacity element, or a piezoelectric oscillator, a mounting portion for the electronic component is provided in a principal surface (usually an upper surface) of an insulating substrate having a rectangular parallelepiped shape, for example, and a wiring conductor is disposed from a lateral surface to a lower surface of the insulating substrate. When an electronic device including the wiring substrate is joined to a mount board with a brazing material, the wiring conductor serves as an external electrode portion.